Modeling and Simulation of the Mechanical Behaviour of Hydrogels

Abstract

Hydrogels are three dimensional crosslinked polymer networks swollen by water molecules. The unique properties of hydrogels lies they can reversibly change shape, volume and/or material properties in response to external stimulus. Dependent on the type of hydrogels, changes in temperature, pH, electric current and light have been studies in their role as stimuli. Due to the active response, hydrogels have potential impact on a large variety of applications including: optical devices, smart adhesion surfaces, drug delivery systems and soft tissue engineering. This thesis first reviews the class of hydrogel models including bi/tri-phasic model, poroelastic model and visco-elastic model. A thermodynamics model which couples large deformation and diffusion is presented. The constitutive model is implemented into Abaqus and finite element analysis is performed in study of the shape evolution of hydrogel thin structures under mechanical loading or inhomogeneous swelling/shrinking. The bifurcation phenomena of hydrogel cap under concentrated loading are examined. Hydrogel micro-gear fabrication is proposed by buckling of multilayered film-hydrogel tubes upon shrinking. Non-trivial three dimensional flower/bowl configurations are obtained through prescribing the material distribution within the hydrogel plate. The corresponding problem is also examined with a modified Von-Karman plate theory. This study also shed light on the formation of patterns in nature like flowers and leaves.